Question

A chemistry student needs 25.0 ml of pentane for an experiment. By consulting the CRC Handbook of Chemistry and Physics, the student discovers that thedensity of pentane is 0.626 g.cm Calculate the mass of pentane the student should weigh out.Be sure your answer has the correct number of significant digits.

Answer 1

To determine the mass of pentane the student should weigh out

Mass - density ratio formula

`\text{Density = }(Mass)/(Volume)`

`\begin{gathered} \text{Density = }(Mass)/(Volume) \\ Mass\text{ of pentane = Density of pentane x Volume of pentane} \\ Density\text{ }of\text{ pentane = 0.626 g.cm} \\ Volume\text{ of pentane = 25ml} \end{gathered}`
`\begin{gathered} 1\text{millilitre = 1 cubic cm } \\ 25ml=25cm^3 \\ \text{volume of pentane = 25cm}^{3^{}} \end{gathered}`
`\begin{gathered} \text{Mass of pentane = Density x Volume} \\ \text{Mass of pentane = 0.626 g. cm x 25 cm}^3 \\ \text{Mass of pentane = 15.65g} \\ \text{Mass of pentane }\cong\text{ 16g } \end{gathered}`

Therefore the answer for the mass of pentane = 16g (1significant figure)